EXPLORATIONS OF EVERYDAY CHEMICAL COMPOUNDS

Monosodium glutamate, or MSG for short, has long been the villain of the food supplement world. In the UK, Chinese takeaways proudly display ‘No MSG’ signs beside their counters, and many websites will purport to tell you ‘the truth about MSG’. Numerous studies have been carried out examining the effects of MSG, but with all the conflicting information, it can be hard for consumers to know who to believe.

MSG was first isolated from seaweed in Japan in 1908. It was said to contribute an ‘umami’ flavour when added to dishes; ‘umami’ is derived from the Japanese word for ‘tasty’. By the mid-20th century, MSG was a commonly used supplement in Japanese and Chinese cuisine, and had also spread to numerous other countries, including the USA, where it was routinely used in restaurants and takeaways across the country.

The term ‘Chinese restaurant syndrome’ was coined by a Chinese-American doctor, Robert Ho Man Kwok, who wrote a letter to a scientific journal complaining of experiencing palpitations and numbness after eating in Chinese restaurants. Kwok didn’t identify any particular component of his meal as causing this effect, but, despite the scarcity of evidence, MSG was quickly fingered as the culprit. A study carried out by a Dr John Olney around the same time found that, when MSG was injected into the brains of mice, it could cause brain damage.

Whilst this may seem concerning, an oft-omitted fact when reporting this study is that Olney used huge quantities of MSG in his studies, up to 4 grams per kilogram of body weight all at once, an amount many times higher than humans are likely to consume as part of a balanced diet. To put this into perspective, in industrialised nations it’s estimated we ingest no more than 1 gram over the course of a day, and often much less. In order to match the highest dosage used in Olney’s tests, we’d have to consume 300g of MSG all at once – a quantity many times more than the amount of MSG found in an average Chinese takeaway meal.

Olney also produced results in primates with high doses of MSG, but these haven’t been replicated by other studies attempting to observe the same results. Whilst this doesn’t completely discount Olney’s observations, replicability is a very important part of scientific testing. Without this, we don’t have convincing proof that high amounts of MSG can cause brain damage in primates, nor can we really state anything about human reactions to MSG from these results.

Another study of interest is one carried out in the 1970s, which for six weeks fed 11 subjects up to almost 150 grams of MSG, and noted no ill effects as a consequence. The fact of the matter is, that despite the plethora of symptoms that MSG has been linked to over the years, there is absolutely no scientific evidence for any of them. Numerous studies and reviews have failed to find any correlation between undesirable symptoms and MSG, and its use as a food supplement is still approved by food regulatory bodies. The few trials that have found links have often been criticised for poor trial design – for example, not having any blinding of testing, so subjects knew that they were ingesting MSG, which could obviously colour their feedback.

Chemically, MSG is simply the sodium salt of glutamic acid, which is a naturally occurring amino acid. Glutamate, the deprotonated form of glutamic acid, is found in tomatoes, ham and cheese, and is chemically the same as MSG – both are treated in exactly the same way by the body. If MSG did cause the symptoms commonly attributed to it, then you’d fully expect eating foods high in glutamate to produce exactly the same effect. Oddly, you don’t tend to hear anyone complaining of ‘Chinese restaurant syndrome’ after eating cheese.

Some people may point to anecdotal evidence of their own, that they’ve experienced allergic reactions to MSG in foods. Well-controlled studies have failed to find a link, however; in one study, in which 71 subjects were administered either MSG or a placebo, only one subject reported a reaction. This subject received the placebo in the test. Many other tests have documented cases where subjects who identify as MSG sensitive react to the placebo test, rather than MSG, suggesting there may also by psychological factors at work. It is suggested that a very small number of people may be sensitive to larger amounts of MSG, but the symptoms of this reaction are mild. Those who complain of MSG sensitivity may also be reacting to some other substance in the food, rather than MSG itself.

Regardless of the scientific evidence, the calls from some quarters to ban MSG from all foods are a little over the top. The possibility of mild reaction in a very small number of people, and only when amounts much higher than those usually present in our diet are ingested, shouldn’t be a cause to ban it as a food additive for the vast majority of consumers for whom it is documented as having no effect. In summary, it’s clear that MSG is somewhat the victim of a character assassination, and we shouldn’t be worrying about the amounts we ingest on a daily basis. However, if you want to read more of the evidence yourself, check out the links supplied in the references section below.

The structures of glutamate/glutamic acid are either unrealistic or just wrong. The structure you have for glutamic acid is the “neutral” structure, which does not exist in any appreciable amount (physiologically the zwitter ion form is most abundant).

The glutamate structure is wrong – the side chain carboxylic acid should be deprotonated (the other one can be deprotonated here, but doesn’t have to be) also at any pH that would deprotonate the acid the amino group would certainly be protonated (NH3+ not NH2).

http://www.compoundchem.com/ Compound Interest

As far as the glutamic acid structure goes, since the graphic isn’t really focused on glutamic acid, I just went for the general structure. I don’t think that this is a problem in the context of the graphic.

As for the structure of the glutamate ion, I concede that I included the structure shown to show the form of the ion in monosodium glutamate, since that’s the primary compound being discussed. Admittedly, in foodstuffs, the ion you describe is correct; and therefore it may be worth changing with clarification.

Tomatoes, ham and cheese are all migraine triggers. Many of the ‘MSG syndrome’ symptoms are also symptoms of migraine. And, turns out, migraine seems to be under-diagnosed.
I’ll give you that there’s no evidence that MSG is universally toxic, but yes, if I (knowingly or unknowingly) eat something with MSG, I get a migraine. As I will if I eat cheese, too much tomato, or preserved meats, among other foods (especially those strong in umami).
I wonder whether the original ‘Chinese restaurant syndrome’ people had usual diets low in migraine triggers.

Personally, larger amounts of MSG, any amount of aspartame, or any amount of Stevia will instantly give me a vicious headache.

http://www.compoundchem.com/ Compound Interest

As it happens, I’m unaffiliated with the American Chemical Society; I’m just a chemistry teacher keen to tackle the common misunderstandings about chemicals, and those about MSG are certainly up there.

The point you make about peanuts and lactose perfectly illustrate my concluding point – that, just because something is considered to have a negative effect on a small number of people, doesn’t mean that it should be immediately banned from use. I’m sure we’d all agree that banning nuts because some people are allergic to them would be ridiculous. I won’t address the other points, as they’re not really overly relevant to a debate about the safety of MSG – we’re not discussing the safety of other chemicals here, but that of MSG, which is independent of the other examples you cite.

You may have noted that the post here didn’t state that MSG never effects anyone negatively; there is some scientific evidence that very high amounts can cause some mild symptoms in a small number of people. That’s exactly what the link you provided concurs with: “Researchers acknowledge, though, that a small percentage of people may have short-term reactions to MSG. Symptoms are usually mild and don’t require treatment.”

It also takes the line adopted in this article, however: “researchers have found no definitive evidence of a link between MSG and these symptoms.” The facts are that a large number of well designed, double blinded studies have failed to find a link. Some of these studies have even deliberately used subjects who identified as MSG sensitive, and yet still failed to show consistent and reproducible reactions to MSG under test conditions – see this review: http://jn.nutrition.org/content/130/4/1058S.short

There is obviously anecdotal evidence of MSG sensitivity, but the reason we require scientific evidence is that it removes all other factors. If MSG can’t be shown in isolation to produce symptoms, then we can’t conclude, scientifically, that it causes any. Aspartame is another which has a bad reputation (bizarrely, far more so in the US than the UK), but again, is something of a victim of a character assassination. What I will say regarding aspartame is that it has been shown to cause problems for those with phenylketonuria, as sufferers are unable to metabolise it; but it’s safe for the majority of the population.